(1) Field of The Invention
This invention relates to gravure printing inks having vehicles containing improved solution rosin resinates. More specifically, this invention relates to improved rosin resinates modified with Group I metals, methods for preparing the modified rosin resinates, as well as use of the modified rosin resinates in vehicles for gravure printing inks.
(2) Description of The Prior Art
A gravure printing ink generally comprises a pigment and a vehicle containing a binder to carry the pigment. There is considerable research to reduce the cost of printing ink binders but in attempting to reduce costs the performance requirements of the ink must be maintained. As the printing arts have developed the speeds of printing have increased and requirements for various ink properties, such as gloss, drying properties, blocking, holdout, film formation, film toughness (resistance to abrasion), reducibility, printability, color development, resistance to static movement or rub, compatibility and stability, are of primary importance to the binder supplier. All of these properties are affected by the binder or resin used to formulate the printing inks.
Rosins have been used as binders in vehicles for printing inks for many years. For example, U.S. Pat. No. 2,299,135 to Erikson, et al.; U.S. Patent No. 2,393,637 to Jones, et al.; and U.S. Pat. No. 4,398,016 each disclose a rosin modified phenolic resin in a vehicle for offset printing inks. The patents to Yoshioha, et al., U.S. Pat. No., 3,468,829 and Rudolphy, et al., U.S. Pat. No. 4,198,329 and the book "Rosin Derivatives For Ink ...," American Ink Maker, F. G. Oswald (1945) each disclose rosin esters used in printing ink formulations.
Historically, among the problems facing a publication gravure ink containing a rosin resinate have been compatibility of the resinate, in particular metal rosin resinates, with cellulosic reinforcing fillers, such as ethyl hydroxy ethyl cellulose (EHEC) solutions and stability of yellow pigment inks. Solutions to these problems have been diametrically opposed. One way to improve EHEC compatibility has been to increase the moisture level in the resinate but yellow pigment is sensitive to moisture and increased moisture levels is detrimental to yellow pigment stability. One way to improve yellow pigment stability is to eliminate the use of zinc in the manufacture of the solution metal resinates which results in loss of EHEC compatibility.
There exists a need in the art of gravure printing inks for an ink which is inexpensive and exhibits high performance characteristics. Also there is need for a gravure printing ink having improved stability with yellow pigment and improved compatibility with ethyl hydroxy ethyl cellulose without diminishing printing quality. Further, there is also a need in the art for more homogeneous printing ink vehicles which exhibits consistent properties.
Accordingly, an object of this invention is to provide gravure printing inks having a vehicle containing rosin resinates improved by being modified with a reactive compound of a metal from Group I of the Periodic Table.
Another object of this invention is to provide a rosin resinate containing a reactive compound of a metal belonging to Group I of the Periodic Table.
A further object of this invention is to provide a process for making modified rosin resinates which are particularly useful as a component of printing ink vehicles.
Other objects, features and advantages of the invention will be apparent from the details of the invention as more fully described and claimed.